1. Field of the Invention
This invention pertains to insulation, and more particularly to apparatus for insulating molten metal.
2. Description of the Prior Art
Various equipment has been designed to insulate molten metal such as metal flowing from a hot ladle in foundry ladles, induction furnaces and other melts. It is essential that the metal remain at a temperature well above the freezing point as it is transferred from the ladle to the desired molds. In some instances, the molten metal is poured into a trough for running therealong to a torpedo car, from which the metal is poured into the molds. The trough must be very well insulated to retain the molten metal well above the minimum pouring temperature as the molten metal flows in the trough. Additionally, it is desirable to cover the metal to contain dust and fumes for pollution control and to control energy loss.
Examples of prior materials for covering troughs and thus reducing undesirable cooling of the molten metal include refractory slabs and metal slabs. Both types of slabs are supported at two opposite edges by suitable sills on opposite sides of the trough. Refractory slabs possess the disadvantage of being very expensive and heavy. The refractory slabs, which may be about 10 to 12 inches thick, require intermediate supports for the span between the trough sills. The supports are usually in the form of metal reinforcing rods extending through the slabs in the direction perpendicular to the flow of the molten metal. Reinforced refractory slabs are not satisfactory because the extremely high temperature of the molten metal causes the reinforcing rods to sag and even melt. As a result, the reinforcing rods do not adequately support the refractory slabs, and the refractory slabs frequently crack.
Metal slabs are unsatisfactory for covering molten metal troughs because they attain a temperature approaching that of the molten metal. The hot metal slabs then radiate excessive heat to nearby foundry equipment and workers . Also, metal slabs sag because of exposure to the hot molten metal and must be periodically replaced.
Thus, a need exists for improved insulation for molten metal flowing in a foundry trough.